The looser the filters, the more the need for the most sophisticated monitoring tools, like those employed at Facebook and those offered by independent companies such as the UK's Crisp Thinking, which works for Lego, Electronic Arts, and Sony Corp's online entertainment unit, among others.
In addition to blocking forbidden words and strings of digits that could represent phone numbers, Crisp assigns warning scores to chats based on multiple categories of information, including the use of profanity, personally identifying information and signs of grooming.
Yet even though defensive techniques are now available and effective they can be expensive.
They can also alienate some of a site's target audience - especially teen users who expect more freedom of expression.'There are companies out there that are doing a very good job, working within the confines of what they have available,' said Brooke Donahue, a supervisory special agent with an FBI team devoted to Internet predators and child pornography.
Under a 1998 law known as COPPA, for the Children's Online Privacy Protection Act, sites directed at those 12 and under must have verified parental consent before collecting data on children.